I suppose that you ever seen http://mathworld.wolfram.com/ or http://www.wolfram.com as a scientist. Wolfram Alpha is the best online tool for evaluation, calculation and some social datas. Wolfram Alpha is based on Mathematica engine and everything is clear, easy and very scientific while using. I deeply suggest to check this tool...
(Here is a search/calculation/evaluation engine used in maths generally.
But it's suggested for everyone who are in science actively.)
